The invention relates to a display device for generating an image which is perceivable, by a viewer of an object located in an object plane, as being superimposed on the object.
Such a device is, for example, an HMD device (Head Mounted Display Device), wherein superposition of the generated image on the object is often referred to as an augmented representation.
There are HMD devices which lack a focusing unit allowing adjustment of the distance from the generated image to the viewer. Such devices are difficult to use particularly for presbyopic older viewers who have a reduced power to accommodate.
Further, HMD devices are known which include a focusing unit to adjust the distance from the generated image to the viewer. However, for this purpose, at least one sufficiently big adjustment knob needs to be provided in the HMD device in order to manually displace lenses and/or an imaging element. If the HMD device is adapted to focus automatically, there is the inescapable additional requirement of a motor drive. This makes the HMD device heavy and cumbersome.
In view thereof, it is an object of the invention to provide a potentially lighter and smaller display device for generating an image which is perceivable, by a viewer of an object located in an object plane, as being superimposed on the object.